Dentifrice composition

ABSTRACT

Dentifrice composition containing a monofluorophosphate and polishing agent containing calcium carbonate and insoluble alkali metal metaphosphate, alumina or mixture therof. The ratio of calcium carbonate to insoluble alkali metal metaphosphate and to alumina is about 3:1 to about 1000:1. This dentifrice retains a desirable level of soluble fluoride upon aging and when insoluble alkali metal metaphosphate is present, does not cause substantial corrosion of unlined aluminum containers.

This application is a continuation-in-part of Ser. No. 176,396 filedSept. 9, 1971, now U.S. Pat. No. 3,864,471, granted Feb. 4, 1975 whichwas filed as a continuation of Ser. No. 848,241, filed Nov. 19, 1969,now abandoned, which was filed as a continuation-in-part of Ser. No.785,731, filed Dec. 20, 1968, now abandoned.

The present invention relates to a dentifrice preparation containing awater-soluble monofluorophosphate salt.

Water soluble monofluorophosphates and particularly alkali metalmonofluorophosphates such as sodium monofluorophosphate have been usedas fluorine-providing active ingredients in dentifrice compositions. Thepolishing agents which may be used in such dentifrices have been thesubject of much investigation.

A dentifrice containing sodium monofluorophosphate and a polishing agentwhich is free of insoluble phosphate salt and which, in fact, is solelycalcium carbonate loses an appreciable amount of the fluorine insolution upon aging.

In order to obtain maximum fluorine-retention of themonofluorophosphate, the prior art has used minor amounts of calciumsalt, such as dicalcium phosphate or calcium carbonate, or magnesiumsalt, and has used as the major polishing agent, insoluble alkali metalmetaphosphate. It has been the general practice in the prior art topackage monofluorophosphate dentifrices in an epoxy lined aluminumcontainer or in lined containers of other metals or in plasticcontainers since components of various monofluorophosphate dentifricescause corrosion of unlined aluminum tubes upon storage.

This invention provides monofluorophosphate dentifrice which has specialadvantages over prior art monofluorophosphate dentifrices containingcalcium carbonate or insoluble alkali metal metaphosphate. Moreparticularly, the dentifrice of the instant invention eliminates theinstability characteristic of prior art monofluorophosphate dentifricecontaining calcium carbonate which is free of insoluble phosphate. Theinvention also provides a monofluorophosphate dentifrice which uponstorage does not cause substantial corrosion of unlined aluminumcontainers.

Other desirable properties will be apparent from consideration of thefollowing specification.

In accordance with certain of its aspects, this invention relates to adentifrice composition comprising a water-soluble monofluorophosphateand a water-insoluble compatible polishing material comprising a mixtureof calcium carbonate and insoluble alkali metal metaphosphate, the ratioof said carbonate to said insoluble alkali metal metaphosphate beingabout 3:1 to about 1000:1.

Such a dentifrice retains a desirable high level of monofluorophosphateas fluoride upon aging and can also be compatibly incorporated intounlined aluminum tubes.

The sodium monofluorophosphate as commercially available may varyconsiderably in purity. It may be used in any suitable purity providedthat any impurities do not substantially adversely affect the desiredproperties. In general, the purity is desirably at least about 80%. Forbest results, it should be at least 85%, and preferably at least 90% byweight of sodium monofluorophosphate with the balance being primarilyimpurities or by-products of manufacture such as sodium fluoride,water-soluble sodium phosphate salt, and the like. Expressed in anotherway, the sodium monofluorophosphate employed should have a totalfluoride content of above 12%, preferably above 12.7%; a content of notmore than 1.5%, preferably not more than 1.2% of free sodium fluoride;and a sodium monofluorophosphate content of at least 12% preferably atleast 12.1%, all calculated as fluorine.

Typically, the monofluorophosphate is present in amount which providesabout 0.01-1% fluorine to the dentifrice. Sodium monofluorophosphate maybe present in amounts of about 0.05% to about 7.6%.

The calcium carbonate of the polishing agent is preferably chalk. Chalkis typically employed in powder form of a size of about 1 to 10 microns.

It is preferred to use a grade of calcium carbonate of relatively highapparent specific gravity, say about 0.9 to 1.2. If desired, calciumcarbonate grades of lower apparent specific gravity, say about 0.7 to0.9, also may be used. "Apparent specific gravity" refers to theuntamped specific gravity of salt.

In accordance with certain aspects of this invention, the minorcomponent of the polishing agent is an insoluble alkali metalmetaphosphate.

The insoluble alkali metal metaphosphates are preferably the insolublesodium and potassium salts of polymetaphosphoric acid. These materialsare known in the art with the insoluble sodium metaphosphate having beensuggested as a polishing agent as previously indicated. Such materialsmay be formed in any suitable manner, as illustrated by Thorpe'sDictionary of Applied Chemistry, vol. 9 (4th ed.), pp. 510-511. Theforms of insoluble sodium metaphosphate known as Madrell's salt andKurrol's salt are further examples of suitable materials. Thesemetaphosphate salts exhibit only a minute solubility in water, and arecommonly referred to as insoluble metaphosphates therefore. There ispresent a minor amount of soluble phosphate material as impurities,usually of the order of a few percent such as up to about 4% by weight.The amount of soluble phosphate material which is believed to be asoluble sodium trimetaphosphate in the case of insoluble sodiummetaphosphate may be reduced by washing with water if desired. Theinsoluble alkali metal metaphosphate is typically employed in powderform of a size such that no more than about 1% of the material is largerthan about 37 microns.

The ratio of calcium carbonate to insoluble alkali metal metaphosphateis about 3:1 to about 1000:1, preferably about 6:1 to about 1000:1, say,about 6:1 to about 500:1, and most preferably about 46.25:1.

At the preferred ratios, particularly when relatively small amounts ofinsoluble alkali metal metaphosphate are employed, the dentifrice doesnot corrode unlined aluminum tubes, almost without exception. Whengreater amounts of the metaphosphate are employed, within the scope ofthe invention, the dentifrice still does not cause substantial corrosionof unlined aluminum tubes, although an exceptional case of some adverseaction on the aluminum may occasionally occur.

The total polishing agent content of the dentifrice is variable, butwill generally be up to about 95%, by weight of the total composition.In the case of a dental cream, such polishing agents will generally beabout 20 to about 75%, whereas in tooth powders the polishing agentswill usually be in greater proportion, such as about 70 to about 95%.

In the preparation of tooth powders, it is usually sufficient to admixmechanically, for example, by milling, the various solid ingredients, inappropriate quantities and particle sizes.

Any suitable surface active or detersive material may be included in thedentifrice compositions. Such compatible materials are desirable toprovide additional detersive, foaming and anti-bacterial propertiesdepending upon the specific type of surface active material and areselected similarly. These detergents are water-soluble organic compoundsusually, and may be anionic, nonionic or cationic in structure. It ispreferred to use the water-soluble non-soap or synthetic organicdetergents usually. Suitable detersive materials are known and include,for example, the water-soluble salts of higher fatty acid monoglyceridemonosulfate detergent (e.g., sodium coconut fatty acid monoglyceridemonosulfate), higher alkyl sulfate (e.g., sodium lauryl sulfate), alkylaryl sulfonate (e.g., sodium dodecyl benzene sulfonate), higher fattyacid esters of 1,2-dihydroxy propane sulfonate (e.g., sodium coconutfatty acid ester of 1,2-dihydroxy propane sulfonate), and the like.

The various surface active materials may be used in any suitable amount,generally from about 0.05 to about 10% by weight, and preferably fromabout 0.5 to 5% by weight of the dentifrice composition.

It is a further embodiment of the present invention to use thesubstantially saturated higher aliphatic acyl amides of lower aliphaticamino carboxylic acid compounds, such as those having 12 to 16 carbonsin the acyl radical, and as more particularly described in U.S. Pat. No.2,689,170, issued Sept. 14, 1954. The amino acid portion is derivedgenerally from the lower aliphatic saturated monoaminocarboxylic acidshaving about 2 to 6 carbons, usually the monocarboxylic acid compounds.Suitable compounds are the fatty acid amides of glycine, sarcosine,alanine, 3-amino-propanoic acid and valine having about 12 to 16 carbonsin the acyl group. It is preferred to use the N-lauroyl, myristoyl andpalmitoyl sarcoside compounds however for optimum effects.

The amide compounds may be employed in the form of the free acid orpreferably as the water-soluble salts thereof, such as the alkali metal,ammonium, amine and alkylolamine salts. Specific examples thereof aresodium and potassium N-lauroyl, myristoyl and palmitoyl sarcosides,ammonium and ethanolamine N-lauroyl sarcoside, N-lauroyl sarcosine, andsodium N-lauroyl glycide and alanine. For convenience herein, referenceto "amino carboxylic acid compound," "sarcoside," and the like refers tosuch compounds having a free carboxylic group or the water-solublecarboxylic salts.

Such materials are utilized in pure or substantially pure form. Theyshould be as free as practicable from soap or similar higher fatty acidmaterial which tends to reduce the activity of these compounds. In usualpractice, the amount of such higher fatty acid material is less than 15%by weight of the amide and insufficient to substantially adverselyaffect it, and preferably less than about 10% of said amide material.

In dental cream formulations, the liquids and solids should beproportioned to form an extrudable creamy mass of desirable consistency.In general, liquids in the dental cream will comprise chiefly water,glycerine, sorbitol, propylene glycol, or the like, including suitablemixtures thereof. It is advantageous usually to use a mixture of bothwater and a humectant such as glycerine or sorbitol. It is preferred touse glycerine. The total liquid content will generally be about 20-75%by weight of the formulation. It is preferred to use also a gellingagent in dental creams such as the natural and synthetic gum andgum-like material, e.g. Irish moss, gum tragacanth, sodiumcarboxymethylcellulose, polyvinylpyrrolidone, starch and the like. TheIrish moss and sodium carboxymethylcellulose are compatible particularlyand are preferred gelling agents as illustrated. The sum content isusually in an amount up to about 10% and preferably about 0.5-5% byweight of the formulation.

In accordance with certain aspects of this invention, desirable agingcharacteristics are obtained when a minor amount of hydrated aluminumoxide (alumina) is in the dentifrice preparation as part of thepolishing agent together with calcium carbonate. The ratio of carbonateto alumina is about 3:1 to about 1000:1. If desired, insoluble alkalimetal metaphosphate may also be a component of the polishing agent. Theratio of the carbonate to insoluble alkali metal metaphosphate alsobeing about 3:1 to about 1000:1. Dentifrices containing small amounts ofinsoluble alkali metal metaphosphate, say where the ratio of calciumcarbonate to the metaphosphate is more than 100:1, have better agingcharacteristics when alumina is also present.

A dental cream having improved physical properties may be prepared fromcalcium carbonate and optionally insoluble alkali metal metaphosphatesuspended in a gel comprising water, humectant and gelling agent, withsaid fluoride compound and organic non-soap synthetic detergent, andhydrated aluminum oxide, said dental cream having pH from about 7 to9.5. If insoluble alkali metal metaphosphate is present, the hydratedaluminum oxide may be omitted. These dental creams exhibit a superiordegree of stability to aging for long periods of time, particularly atelevated temperatures. The aluminum oxide acts as a stabilizing andmodifying agent so as to eliminate or inhibit any tendency forseparation or syneresis of the dental cream in the collapsible tube.

The preferred ratio of calcium carbonate to alumina is about 3:1 to100:1, and most preferably about 35:1 to about 52:1.

In the instant invention sufficient insoluble alkali metal metaphosphateand/or alumina is present to substantially prolong the period of timeduring which the monofluorophosphate remains substantially soluble,e.g., to insure that at least, and preferably more than, about 40%, andmost preferably at least 50% of the original monofluorophosphate contentremains soluble after accelerated aging of the dentifrice for 9 weeks at49°C.

Suitable examples of hydrated aluminum oxide which may be employed arethe forms known as alpha and beta aluminum oxide trihydrate and mixturesthereof. It is used usually in the form of fine particles of any desiredparticle size in the manufacture of the dental cream. In practice, it ispreferred to use the alpha trihydrate form of which at least about 90%of the particles pass through on a U.S. standard No. 325 mesh sieve andnot more than about 5% of the particles by weight are less than 5microns. It has been found that amounts of hydrated aluminum oxide fromabout 1/4 to about 10% by weight are most desirable and preferably about1% by weight of the dentifrice composition.

Various other materials may be incorporated in the oral preparations ofthis invention. Examples thereof are coloring or whitening agents,preservatives, silicones, chlorophyll compounds, ammoniated materialssuch as urea, diammonium phosphate and mixtures thereof, and otherconstituents. These adjuvants are incorporated in the instantcompositions in amounts which do not substantially adversely affect theproperties thereof.

For some purposes it may be desirable to include antibacterial agents inthe compositions of the present invention. Typical antibacterial agentswhich may be used in amounts of about 0.01% to about 5%, preferablyabout 0.05% to about 1.0%, by weight of the dentifrice compositioninclude:

N¹ -4(chlorobenzyl)-N⁵ -2,4-dichlorobenzyl) biguanide;

p-chlorophenyl biguanide;

4-chlorobenzhydryl biguanide;

4-chlorobenzhydrylguanylurea;

N-3-lauroxpropyl-N⁵ -p-chlorobenzylbiguanide

1,6-di-p-chlorophenyl biguanidohexane;

1-(lauryldimethylammonium)-8-(p-chlorobenzyldimethylammonium) octanedichloride;

5,6-dichloro-2-guanidinobenzimidazole;

N¹ -p-chlorphenyl-N⁵ -laurylbiguanide;

5-amino-1,3-bis(2-ethylhexyl)-5-methylhexahydropyrimidine;

and their non-toxic acid addition salts.

Any suitable flavoring or sweetening materials may be employed informulating a flavor for the compositions of the present invention.Examples of suitable flavoring constituents include the flavoring oils,e.g., oils of spearmint, peppermint, wintergreen, sassafras, clove,sage, eucalyptus, marjoram, cinnamon, lemon and orange, as well asmethylsalicylate. Suitable sweetening agents include sucrose, lactose,maltose, sorbitol, sodium cyclamate and saccharine. Suitably, flavor andsweetening agent may together comprise from about 0.01 to 5% or more ofthe compositions of the instant invention.

The dental creams should have a pH practicable for use. A neutral basicpH is particularly desirable. The initial pH range of about 7 to 9.5preferably 7.5 is considered the most practicable for use. Whenreference is made to pH herein, it is intended that such pHdetermination be made on the dental cream directly. If necessary, basicmaterials may be added to adjust the pH as desired.

The container in which the dentifrice composition is placed is typicallya tube from which the dental cream can be extruded. A particularlydesirable aspect of the invention is the fact that the dentifricecomposition including insoluble alkali metal metaphosphate can bedesirably packaged in an unlined aluminum container and exhibitdesirable cosmetic and rheological properties upon storage withoutcausing substantial layer formation or corrosion of the aluminum withwhich it is contacted.

The most desirable results have been obtained when the dentifricecontains about 0.1 to 3% by weight of insoluble alkali metalmetaphosphate and about 44 to 47% by weight of calcium carbonate.

For standardized test purposes in determining the amount of the originalmonofluorphosphate content present in accelerated aging tests, thedentifrice formulations are prepared with about 0.76% of sodiummonofluorophosphate and then tested.

The following specific examples are further illustrative of the natureof the present invention, but it is to be understood that the inventionis not limited thereto. The compositions are prepared in the usualmanner and all amounts of the various ingredients are by weight unlessotherwise specified.

EXAMPLE 1

The following dental creams are prepared:

                     Parts                                                                         A        B                                                   ______________________________________                                        Sodium monofluorophosphate                                                                       0.76       0.76                                            Calcium carbonate  52.00      46.25                                           Insoluble sodium metaphosphate                                                                   --         1.00                                            Glycerine          22.00      22.00                                           Sodium carboxymethylcellulose                                                                    0.95       1.30                                            Hydrated alumina   --         1.00                                            Sodium N-lauryl sarcosinate                                                                      2.00       2.00                                            Sodium benzoate    0.50       0.50                                            Sodium saccharine  0.20       0.20                                            Flavor             0.90       0.90                                            Water              q.s. to    q.s. to                                                            100        100                                             ______________________________________                                    

Composition A in which no phosphate salt polishing agent is present andcalcium carbonate is the sole abrasive and Composition B containingcalcium carbonate, alumina and phosphate salt are aged at 49°C. and thepercentage of soluble monofluorophosphate present as fluoride isdetermined periodically. Each three weeks under this aging conditioncorresponds to about 1 year's aging at room temperature. The results areindicated in the table below:

           % Soluble Monofluorophosphate as                                              Fluoride-49°C.                                                         WEEKS                                                                  Composition                                                                            0         3         6       9                                        ______________________________________                                        A        0.09      0.07      0.03    0.01                                     B        0.09      0.08      0.08    0.07                                     ______________________________________                                    

Thus, it is clear from these results that the addition of a small amountof the insoluble metaphosphate and alumina markedly increases theability of Composition B to retain soluble fluorine.

When composition B is placed in an unlined aluminum tube, the aluminumsurface in contact with the dentifrice remains substantially free fromcorrosion even over a prolonged period of time.

EXAMPLE 2

The following dentifrices also have high retention of solublemonofluorophosphate as fluorine and do not cause a substantial degree ofcorrosion of the aluminum surface with which they are contacted inunlined aluminum tubes.

    ______________________________________                                                        C      D        E                                             ______________________________________                                        Sodium monofluorophosphate                                                                      0.76     0.76     0.76                                      Calcium carbonate 40.15    44.25    47.15                                     Insoluble sodium metaphosphate                                                                  7.10     3.00     0.10                                      Glycerine         22.00    22.00    22.00                                     Sodium carboxymethylcellulose                                                                   1.20     1.30     1.30                                      Hydrated alumina  1.00     1.00     1.00                                      Sodium N-lauryl sarcosinate                                                                     2.00     2.00     2.00                                      Sodium benzoate   0.05     0.05     0.05                                      Sodium saccharine 0.20     0.20     0.20                                      Flavor            0.90     0.90     0.90                                      Water             q.s. to  q.s. to  q.s. to                                                     100      100      100                                       ______________________________________                                    

EXAMPLE 3

The following dentifrices are also within the scope of the invention:

                    F      G        H                                             ______________________________________                                        Sodium monofluorophosphate                                                                      0.76     0.76     0.76                                      Calcium carbonate 35.25    47.20    46.00                                     Insoluble sodium metaphosphate                                                                  12.00    0.05     1.00                                      Glycerine         22.00    22.00    22.00                                     Sodium carboxymethylcellulose                                                                   1.20     1.30     1.30                                      Hydrated alumina  1.00     1.00     --                                        Sodium N-lauroyl sarcosinate                                                                    2.00     2.00     2.00                                      Sodium benzoate   0.50     0.50     0.50                                      Sodium saccharine 0.20     0.20     0.20                                      Flavor            0.90     0.90     0.90                                      Water             q.s. to  q.s. to  q.s. to                                                     100      100      100                                       ______________________________________                                    

EXAMPLE 4

The following dentifrices are prepared:

                    I      J        K                                             ______________________________________                                        Glycerine         22.00    22.00    22.00                                     Sodium Benzoate   0.50     0.50     0.50                                      Sodium saccharine 0.20     0.20     0.76                                      Sodium monofluorophosphate                                                                      0.76     0.76     0.76                                      Hydrated alumina  --       52.00    1.00                                      Calcium carbonate 52.00    --       52.00                                     Sodium carboxymethyl                                                          cellulose         0.95     0.95     0.95                                      Sodium N-lauroyl sarcosinate                                                                    2.00     2.00     2.00                                      Flavor            0.80     0.80     0.80                                                        q.s. to  q.s. to  q.s. to                                                     100      100      100                                       ______________________________________                                    

Each of the dentifrices are aged at 49°C. with the percentage ofmonofluorophosphate determined periodically. The results are indicatedin the table below:

           % Soluble Monofluorophosphate                                                 as fluoride-49°C.                                               Composition                                                                            Weeks                                                                       0       3         6         9                                          ______________________________________                                        I        0.09      0.07      0.03    0.01                                     J        0.09      0.06      0.05    0.04                                     K        0.09      0.08      0.07    0.07                                     ______________________________________                                    

Thus, it is clear that composition K retains soluble fluorine betterthan compositions I and J.

EXAMPLE 5

The following dentifrices are also within the scope of the invention:

    Parts                                                                                        L         M                                                    ______________________________________                                        Sodium monofluorophosphate                                                                     0.76        0.76                                             Glycerine        22.00       22.00                                            Sodium benzoate  0.50        0.50                                             Sodium saccharine                                                                              0.20        0.20                                             Hydrated alumina 13.00       1.50                                             Calcium carbonate                                                                              39.00       52.50                                            Sodium carboxymethyl                                                          cellulose        0.95        0.95                                             Sodium N-lauroyl                                                              sarcosinate      2.00        2.00                                             Flavor           0.80        0.80                                             Water            q.s. to     q.s. to                                                           100         100                                              ______________________________________                                    

EXAMPLE 6

The following dentifrices are also within the scope of the invention:

                    Parts                                                                         N      O        P                                             ______________________________________                                        Sodium monofluorophosphate                                                                      0.76     0.76     0.76                                      Calcium carbonate 35.25    42.25    44.25                                     Insoluble Sodium meta-                                                        phosphate         12.00    5.00     3.00                                      Glycerine         22.00    22.00    22.00                                     Sodium carboxymethyl                                                          cellulose         1.20     1.30     1.30                                      Hydrated alumina  1.00     1.00     1.00                                      Sodium N-lauroyl sarcosinate                                                                    2.00     2.00     2.00                                      Sodium benzoate   0.50     0.50     0.50                                      Sodium saccharine 0.20     0.20     0.20                                      Flavor            0.90     0.90     0.90                                      Water             q.s.     q.s.     q.s.                                                        to 100   to 100   to 100                                    ______________________________________                                    

In addition to sodium monofluorophosphate, Na₂ PO₃ F, othermonofluorophosphate salts which have sufficient water solubility for usein the instant invention include calcium monofluorophosphate, magnesiummonofluorophosphate and aluminum monofluorophosphate. In accordance withthis invention the term "monofluorophosphate" also includesmonofluoropolyphosphates such as Na₄ P₃ O₉ F, K₄ P₃ O₉ F, (NH4)₄ P₃ O₉F, Na₃ KP₃ O₉ F, (NH₄)₃ NaP₃ O₉ F and Li₄ P₃ O₉ F.

It will be apparent to one skilled in the art that modifications of theabove examples may be made thereto.

We claim:
 1. A dental cream composition comprising a water-solublemonofluorophosphate in amount which provides about 0.01-1% by weightfluorine to the dentifrice and about 20-75% by weight of awater-insoluble compatible polishing material consisting essentially ofa mixture of calcium carbonate with insoluble alkali metalmetaphosphate, the ratio of said calcium carbonate to said insolublealkali metal metaphosphate being about 3:1 to about 1000:1;--saiddentifrice having an initial pH of about 7 to 9.5.
 2. The dental creamcomposition claimed in claim 1 wherein said water-solublemonofluorophosphate is sodium monofluorophosphate.
 3. The dental creamcomposition claimed in claim 2 wherein said monofluorophosphate ispresent in an amount of about 0.76% by weight.
 4. The dental creamcomposition claimed in claim 2 wherein said insoluble alkali metalmetaphosphate is insoluble sodium metaphosphate.
 5. The dental creamcomposition claimed in claim 4 wherein the ratio of said calciumcarbonate to said insoluble sodium metaphosphate is about 6:1 to about1000:1.
 6. The dental cream composition claimed in claim 4 wherein theratio of said calcium carbonate to said insoluble sodium metaphosphateis about 46.25:1.